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This study is focused on the detailed examination of the combustion properties and kinetic analysis of a cellulose acetate fibrous bundle (CAFB), separated from used cigarette filters. It was shown that the faster rate of CAFB heating allows a large amount of heat to be supplied to a combustion system in the initial stages, where the increase in heating rate has a positive response to ignition behavior. The best combustion stability of CAFB is achieved at the lowest heating rate. Through the use of different kinetic methods, it was shown that combustion takes place through two series of consecutive reaction steps and one independent single-step reaction. By optimizing the kinetic parameters within the proposed reaction models, it was found that the steps related to the generation of levoglucosenone (LGO) (by catalytic dehydration of levoglucosan (LG)) and acrolein (by breakdown of glycerol during CAFB burning—which was carried out through glycerol adsorption on a TiO2 surface in a the developed dehydration mechanism) represent rate-controlling steps, which are strongly controlled by applied heating rate. Isothermal predictions have shown that CAFB manifests very good long-term stability at 60 °C (which corresponds to storage in a sea shipping container), while at 200 °C, it shows a sudden loss in thermal stability, which is related to the physical properties of the sample. [ABSTRACT FROM AUTHOR]

Thermo-chemical conversion of cigarette butt filters (CBF) waste was investigated using various thermal analysis techniques (simultaneous TG-DTG-DTA and DSC methods) at different heating rates in an inert atmosphere. Thermo- and thermophysical properties of waste material were discussed, from the point of view of chemical structure and the influence of experimental parameters on the conversion process. It was established that acetyl groups of plasticizer (triacetin) interact with cellulose acetate through dipolar interactions and hydrogen bonding's. Influence of these polar interactions can affect the position of glass transition temperature, Tg, of CBF. Based on estimated value of Tg from DSC analysis, it was found that cellulose acetate present in CBF has degree of substitution equals to 2.8, where the presence of cellulose triacetate was confirmed. It was assumed that an increase of degree of substitution leads to decline in the crystallinity. A decline of crystallinity causes the reduction of hydroxyl groups, leading to less organized chains, and whereby decreasing of inter-molecular interactions through hydrogen bonding. Based on the examination of thermophysical characteristics of the tested material, it was found that both, the heat capacity and the thermal inertia of material linearly increase with temperature, during pyrolysis progression. It was concluded that the type of bio-char produced in this process would have a large capacity to store the heat, which may depend on the formed particles size diameter and porosity. Furthermore, it was inferred that magnitude drops of thermal conductivity, κ, after Tg depends on the material fibrillation. [ABSTRACT FROM AUTHOR]

Thermo-chemical conversion via the pyrolysis of cigarette butt (CB) filters was successfully valorized and upcycled in the pre-carbonization and carbonization stages. The pre-carbonization stage (devolatilization) of the precursor material (cellulose acetate filter, r-CAcF) was analyzed by micro-scale experiments under non-isothermal conditions using TG-DTG-DTA and DSC techniques. The results of a detailed kinetic study showed that the decomposition of r-CAcF takes place via complex mechanisms, including consecutive reaction steps and two single-step reactions. Consecutive stages include the α-transition referred to as a cellulose polymorphic transformation (cellulose I → II) through crystallization mechanism changes, where a more thermodynamically ordered system was obtained. It was found that the transformation rate of cellulose I → II ('cellulose regeneration') is strongly affected by the presence of alkali metals and the deacetylation process. Two single-step reactions showed significant overlapping behavior, which involves a nucleation-controlled scission mechanism (producing levoglucosan, gaseous products, and abundant radicals) and hydrolytic decomposition of cellulose by catalytic cleavage of glycosidic bonds with the presence of an acidic catalyst. A macro-scale experiment showed that the operating temperature and heating rate had the most notable effects on the total surface area of the manufactured carbon. A substantial degree of mesoporosity with a median pore radius of 3.1695 nm was identified. The presence of macroporosity on the carbon surface and acidic surface functional groups was observed. [ABSTRACT FROM AUTHOR]